1. Field of the Invention
The invention generally relates to a protection device, in particular, to an electrostatic protection device.
2. Description of Related Art
The electrostatic discharge (ESD) is a phenomenon of the electrostatic movement on a non-conductor. The phenomenon causes damages in an integrated circuit. For example, when a common charged body, such as a machine for packaging the integrated circuit or an instrument for testing the integrated circuit, touches a chip, the electrostatic charges are produced. At the moment, the electrostatic charges may cause damages to the integrated circuit in the chip.
For preventing the damages of the integrated circuit which is affected by the ESD from the outside thereof, an electrostatic discharge protection circuit is usually implemented in the integrated circuit. In a silicide process, a common electrostatic discharge protection is implemented with a silicide block on an n-type transistor to have a property of uniform turn-on while the electrostatic discharge occurs. Furthermore, a more completed discharging path is offered. Nevertheless, the additional silicide block increases the complex and the cost of the fabrication process.
For improving the drawback described above, most of the electrostatic discharge protection devices now already remove the silicide block, and use a control circuit to control an n-type transistor instead. However, this kind of design must include a good control circuit to turn on the n-type transistor properly. Besides, the control circuit is usually affected by noises, and further causes the electrostatic discharge protection device to work abnormally.